linux-kernel - Re: [PATCH 2/2] iommu/arm-smmu-v3: simplify parse_driver

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Date:   Thu, 9 Jan 2020 13:41:56 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] iommu/arm-smmu-v3: simplify parse_driver_options()

On 26/12/2019 9:51 am, Masahiro Yamada wrote:
> Using ARRAY_SIZE() instead of the sentinel is slightly simpler, IMHO.

Given that it's fairly well-decided that we don't want to add any more 
of these anyway, I'd be inclined to lose the array/loop machinery 
altogether. As it is we'd need a lot more options for it to actually 
offer any kind of code size saving.

Robin.

> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
> 
>   drivers/iommu/arm-smmu-v3.c | 7 +++----
>   1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index ed9933960370..b27489b7f9d8 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -676,7 +676,6 @@ struct arm_smmu_option_prop {
>   static const struct arm_smmu_option_prop arm_smmu_options[] = {
>   	{ ARM_SMMU_OPT_SKIP_PREFETCH, "hisilicon,broken-prefetch-cmd" },
>   	{ ARM_SMMU_OPT_PAGE0_REGS_ONLY, "cavium,cn9900-broken-page1-regspace"},
> -	{ 0, NULL},
>   };
>   
>   static inline void __iomem *arm_smmu_page1_fixup(unsigned long offset,
> @@ -696,16 +695,16 @@ static struct arm_smmu_domain *to_smmu_domain(struct iommu_domain *dom)
>   
>   static void parse_driver_options(struct arm_smmu_device *smmu)
>   {
> -	int i = 0;
> +	int i;
>   
> -	do {
> +	for (i = 0; i < ARRAY_SIZE(arm_smmu_options); i++) {
>   		if (of_property_read_bool(smmu->dev->of_node,
>   						arm_smmu_options[i].prop)) {
>   			smmu->options |= arm_smmu_options[i].opt;
>   			dev_notice(smmu->dev, "option %s\n",
>   				arm_smmu_options[i].prop);
>   		}
> -	} while (arm_smmu_options[++i].opt);
> +	};
>   }
>   
>   /* Low-level queue manipulation functions */
>